Human Spleen Histone H1. Isolation and Amino Acid Sequences of Three Minor Variants, H1a, H1c, and Hid1

Abstract

Following the previous determination of the main variant H1b of human spleen histone H1, we have determined the complete amino acid sequence of another variant, H1d. Limited chymotryptic digestion of H1d produced four fragments, I to IV, and one partial fragment I-II, as in the case of H1b. These fragments were aligned with two overlapping peptides, produced by another enzyme from the intact H1d. We also confirmed the C-terminal sequence of H1d by carboxypeptidase digestion. This H1d has an acetylated N-terminal serine, equimolar alanine or valine residue at 17, and is composed of 212 residues. The molecular weight was 21,233 for the alanine variant and 21,261 for the valine variant in the unmodified form. We also deduced the total sequences of H1a and H1c in a similar way, considering the maximum homology with H1b and H1d. Each N-terminal serine residue is acetylated, too. H1a consists of 222 amino acid residues and has a molecular weight of 22,178 in its unmodified form; the H1c consists of 220 residues and has a molecular weight of 22,218 in that form. The human spleen H1 sequences varied to about the same extent in the N-terminal 40 and C-terminal 110 residues. However, the sequences of the about 70 internal residues are well conserved between the variants. The extent of differences among the human H1 variants is similar to, or rather smaller than, those among the mammalian somatic H1 species. The implications of these differences in the sequence for H1 function are discussed from the evolutionary viewpoint.

Quantitative Mass Spectrometry Reveals that Intact Histone H1 Phosphorylations are Variant Specific and Exhibit Single Molecule Hierarchical Dependence

“…The relative abundance of each proteoform at different phases of the cell cycle was determined as validation of our previously reported phospho-H1 profiling of breast cancer cells (33). We also report the identification of an amino acid substitution A18V on H1.2, which has been previously observed twice by hydrophilic interaction liquid chromatographic (HILIC) methods (53,54). However, it has never been reported by top-down mass spectrometry at the intact protein level and never in MCF-10A cells.…”

Characterization of the Mitotic Specific Phosphorylation Site of Histone H1

“…Sequence analysis demonstrated that the mitotic specific phosphorylation site of CHO H1 is on the end of the N-terminal tail and (Liao and Cole, 1981), rat liver (Cole et al, 1990), human spleen (Ohe et al, 1986(Ohe et al, , 1989, mouse (Yang et al, 1987), rabbit thymus (Rall and Cole 1971;Jones, et al, 1974), and human placenta (Parseghian et al, 1994) were compared with that from CHO (first line in panels B and C). In these comparisons the asterisk indicates that the amino acid in that position is the same as that in CHO H1.…”

The Surprising Composition of the Salivary Proteome of Preterm Human Newborn

“…However, the theoretical Mav of histone H1c is 22,219 Da, 146 Ϯ 4 Da less than the experimental value. Different isoforms of H1 histone have been detected in the spleen of adult subjects (21). Thus, we may hypothesize either that the preterm newborn protein could be an unknown variant of histone H1c or that not characterized PTMs are present in the mature protein.…”